Traumatic brain injury (TBI) is the most common cause of disability in young adults. While much of this disablement is attributable to mental difficulties, the brain mechanisms underlying these difficulties are poorly understood. There is tremendous variability in TBI effects even among patients with similar injury characteristics. This wide range of behavioral outcomes implies variability in neural reorganization supporting these mental operations. We will explore the neural correlates of mental functioning following TBI with functional magnetic resonance imaging (fMRI), a technique for studying dynamic brain function (i.e., functional neuroanatomy). Our focus is on executive functioning and memory, the primary cognitive deficits affecting real-life adjustment following TBI. The activation tasks will include two measures of response inhibition and three measures of memory. The functional neuroanatomy of response inhibition will also be examined pre- and post-rehabilitation using a training program that targets executive deficits. Each experiment capitalizes on an established paradigm from our previous behavioral research with brain-injured patients or our functional neuroimaging research with healthy adults. In addition to standard image analysis techniques emphasizing local brain activations, we will employ multivariate techniques that stress functional interactions across the brain. These techniques are necessary to characterize the task- and performance-related chances in brain connectivity fundamental to the neuropathology of TBI. These studies should impact the direct care of patients with TBI through the development of diagnostic imaging techniques that can be used to characterize brain-behavior relationships and assess functional neuroanatomical changes due to natural recovery and rehabilitation. Moreover, we expect these findings to increase the understanding of neural changes (i.e., neural compensation or re-organization) in response to brain injury in general.